Windows only: Programmer's Notepad is a free Notepad replacement with features aimed towards those who spend their days dealing with code. On top of the basic functionality afforded by Notepad, Programmer's Notepad has code outlining, docking toolbars, tags, interactive error finding—clicking on an output error will jump you to the section of code that generated it—, quick search, syntax highlighting, and a user customizable interface which can be exported via xml files. For another notepad replacement that has recieved accolades from code-writing readers here, check out Notepad++. Programmer's Notepad is freeware, Windows only.